title: Oxidation of catechin and rutin by pentaammineruthenium(III) complexes.
abstract: The reaction of catechin and rutin with Ru(NH(3))(5)L(3+) (L = N-methylpyrazinium (pzCH(3)(+)), pyrazine (pz), and isonicotinamide (isn)) complexes underwent a two-electron oxidation on the catechol ring (B ring) with the formation of quinone products. The kinetics of the oxidation, carried out at [H(+)] = 0.01-1.0 M and pH = 4.0-7.6, suggested that the reaction process involves the rate determining one-electron oxidation of the flavonoids in the form of H(2)X (k(0)), HX(-) (k(1)), and X(2-) (k(2)) by Ru(NH(3))(5)L(3+) complexes to form the corresponding semiquinone radicals, followed by the rapid scavenge of the radicals by the Ru(III) complexes. The specific rate constants (k(0), k(1), and k(2)) were measured and the results together with the application of the Marcus theory were used to estimate the self-exchange parameters for the one-electron couples of the flavonoids, H(2)X/H(2)X(+*), HX(-)/HX(*), and X(2-)/X(-*).
authors.affiliation: Department of Chemistry, Tunghai Christian University, Taichung, Taiwan, ROC.
authors.forename: Jay
authors.initials: J
authors.lastname: Sung
authors.forename: Kai-Sheng
authors.initials: KS
authors.lastname: Huang
authors.forename: Tan-Ju
authors.initials: TJ
authors.lastname: Lai
authors.forename: Yu-Yi
authors.initials: YY
authors.lastname: Chen
authors.forename: Chih-Yeh
authors.initials: CY
authors.lastname: Lin
authors.forename: Andrew
authors.initials: A
authors.lastname: Yeh
authors.forename: Dacheng
authors.initials: D
authors.lastname: Wu
mesh_terms: D002392:Catechin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*; D012431:Rutin / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D012431:Rutin; D012428:Ruthenium; D002392:Catechin